CLASS: SS2

SUBJECT: BIOLOGY                                PERIODS (3)

DURATION: 45MINUTES

TOPIC: FEEDING HABITS

SUBTOPIC 1: CATEGORES OF FEEDING HABITS

SUBTOPIC 2: MECHANISM OF FEEDING HABITS

SUBTOPIC 3: MODIFICATION IN ORGANISMS TO REFLECT FEEDING

PREVIOUS KNOWLEDGE: Studetns are familiar with the topic

OBJECTIVES: At the end of the period(s) students should be able to:

Period 1:

  1. List the different categories of feeding habits
  2. Discuss the different categories of feeding habits.

Period 2: Discuss the modifications and mechanisms of feeding of living organisms

Period 3: Draw the mouthparts of different organisms modified for their mode of feeding.

 

References: Essential Biology for Senior secondary school pages 1-3, pages 115 – 119, 272 – 274

CONTENT: Living organisms exhibit different feeding habits.

 

They are as follows:

  1. Fluid feeding: Fluid feeders feed on any fluid materials and there are two major groups namely
  2. Wallowers – These organisms rest within (wallow) in their food e.g. tapeworm in man’s intestine whichlives in the digested food of its host (hooks and suckers) and absorbs the food directly into its body, using its entire body surface. It has no alimentary canal.
  3. Suckers These organisms feed by sucking fluid from plants and animals. They possess piercing mouthparts (proboscis) Examples of suckers include mosquito, butterfly, bug, tsetse fly, housefly and aphid.
  4. FIlterfeeding: can also be referred to as microphagous feediers. These organisms feed on very tiny organisms which cannot be easily picked. Filter feeders are mainly aquatic animals and they have to wallow in water through sieve like structure into their body in order to collect enough food. Examples include mosquito larva, duck, prawn, mussel.

Mosquito larv make use of mouth brushes (2 small ciliated appendages) and horny aws to create water current and filter planktons (Small colloidal particles) into their mouth.

 

  1. Saprophytic feeding – are mainly non green plants which do not have chloroplasts. They feed on dead and decaying organic matter usng hyphae through which they pour out digestive enzyemes. They digest their food extracellularly and then absorb. Examples are mucour, mushroom and rhizopus.
  2. parasitic feeding: These are organisms that are structurally modified to depend partially or completely on either living organism for their food and survival. Examples include cassytha, mistletoe, dodder (plant parasites) liver fluke, roundworm, tapeworm, tick, louse, guinea worm etc.

 

Living organisms possess different modifications and mechanisms of feeding. These feeding mechanisms are:

  1. Biting and chewing mechanism – The mouthpart are modified for biting and chewing. The mouthparts are:
  2. The Upper lip (labrum) prevents the food from falling off
  3. The lower lip (labium) prevents food wastage from the mouth.

iii.      Mandibles – a pair of heavy, toothed and jaw like structures used for cutting and chewing food

  1. Maxillae-=a pair of maxillae which acts as a biting blade.

Maxillae breaks down the food broken (chewed) into small pieces by the mandibles.

 

Examples of organisms are cockroach and grasshopper

  1. Sucking mechanism – housefly feeds on liquid food so possess enlarged labella (for sucking) with which it sucks up liquid food. The labella have fine channels which allow rapid absorption of liquid food. Housefly sucking mechanism is called sponging in which the mouth is placed on the liquid food and it will goush into the mouth

 

butterfly possess a long, coiled proboscis used for sucking nectars which can be recoiled after use or not in use. Mosquito possess proboscis for sucking blood. The mouth parts form a strong stylet capable of penetrating the skin to suck blood. The mouth produce saliva which prevent blood clotting while it is being sucked in and the labium can be folded back easily to allow the stylet to penetrate skin and suck blood.

iii.      Absorbing mechanism – this type is usually used by endoparasites e.g. tapeworm. It possesses no mouth or alimentary canal but absorb digested food from its host’s intestine with its entire body surface. Tapeworm use hooks and suckers to attach to the intestinal wall to avoid dislodgement. The flat body surface provides a large surface area for absorption and thick cuticle which resists the digestive enzymes of the host.

  1. Trapping and absorbing mechanism: This type of mechanism can be found among carnivorous or insectivorous plants e.g. bladderwort and sundew.
  2. Grinding mechanism: This type of mechanism is common among mammals e.g. man, sheep, goat, cattle etc which grinds their food before swallowing. The grinding is aided by hard and strong teeth made of enamel and dentine. They possess different sets of teeth (Incisors, canine, premolar and molar)

 

INSTRUCTION MATERIALS – Different animal specimens

Teaching methods procedures

Step 1: Teacher introduces the new topic after revising the previous topic with the students

Step II: Teacher mentions and explains the types of feeding habits

Step III: Teacher lists and explains the  mechanism adopted by different organisms for their feeding

Step IV: Teacher allows students to ask questions and writes notes under content on the board

 

CLASSROOM (ACTIVITIES)

PERIOD 1: Students discuss feeding habits of organisms.

Period 2: Students with the guidance of the teacher discuss the feeding mechanism of living organisms

EVALUATION;

Period 1: What is filter feeding?

Period 2: Explain how a butterfly feeds?

SUMMARY/CONCLUSION – TEACHER summariezes the topic, marks the students notes and makes corrections where necessary.